M. Wajid Khan

Influence of substituted benzothiazoles on corrosion in acid solution

Compounds such as 2-aminobenzothiazole (ABT), 2-amino-6-chlorobenzothiazole (ACLBT), 2-amino-6-methyl benzothiazole (AMEBT) and 2-amino-6-methoxy benzothiazole (AMEOBT) have been synthesized and their inhibitive action on the corrosion of mild steel in 1 m HCl has been evaluated using weight loss, potentiodynamic polarization studies and hydrogen permeation measurements. Determination of inhibition efficiency in the presence of these compounds at different temperatures clearly indicates that ACLBT shows the best performance, even at a temperature as high as 60°C. Potentiodynamic polarization studies reveal the fact that ABT and its derivatives act as cathodic inhibitors. All these compounds are found to reduce the permeation of hydrogen through mild steel in HCl solution. The adsorption of these compounds on mild steel from HCl solutions obeys Temkins adsorption isotherm. The adsorption of 2-amino benzothiazole on the mild steel has been substantiated by Auger electron spectroscopy.

Effects of intermittent ozone exposures on powdery mildew of cucumber

Abstract Exposure of plants to O3 may influence foliar diseases caused by fungi. It is hypothesized that concentrations of O3 at or below economic threshold may enhance severity of the fungal disease, whereas higher levels may decrease the severity. To test this hypothesis, effects of intermittent exposures at 50, 100 and 200 ppb O3 and powdery mildew infection by Sphaerotheca fuliginea, using pre-, post- and concomitant-inoculation exposures were investigated on cucumber in closed-top exposure chambers. For impact assessment, plant growth, flowering, fruit-setting, foliar ozone injury, fungal colonization, conidia size and their germination were considered. Ozone (except 50 ppb) caused necrotic lesions on leaves and reduced the plant growth and fruit-setting of cucumber. Plants inoculated with S. fuliginea conidia developed powdery colonies in the intercostal region of leaves. Ozone injury was relatively moderate on fungus-inoculated plants. Powdery mildew development was, however, severe on the plants exposed to 50 ppb O3, but at higher concentrations there was significant decline in fungus colonization. Conidia examined from such plants (exposed to 100 or 200 ppb) were smaller in size and contained fewer fibrosin bodies and showed poor germination. Ozone exposures at 50 ppb, however, stimulated the conidial germination. In an in–vitro experiment, the conidia directly exposed to ozone on glass slides showed more or less similar response to the gas. Ozone at 50 ppb and S. fuliginea interacted synergistically and caused significantly greater decrease in the number of fruits/plant. At 200 ppb O3, the mutual effects were antagonistic. Fungus infection provided partial protection to plants against 200 ppb ozone, and mildew infection was also mild.

Single and interactive effects of O3 and SO2 on tomato

Abstract The stomata are main portals for the diffusion of gaseous pollutants into leaf tissue. We hypothesize that the open-closing response of stomata to gases may determine sensitivity of plants to pollutant(s) and that stomata would open wider in pollutant-injured plants. We also hypothesize that the nature of the interaction between O3 and SO2 on tomato would be governed by the concentrations of the gases. Tomato plants were exposed in exposure chambers to all possible combinations of 0.0, 0.05, 0.1 and 0.2 ppm of O3 and SO2 for 3 hr every third day on 27 occasions in 1988 and 1992. O3 and SO2 at 0.2 ppm induced chlorotic and necrotic lesions, and browning, respectively, on leaves. The sympoms were in traces at 0.1 ppm, while absent at 0.05 ppm of either gas. The degree of foliar injury, based on visual assessment, was considerably higher on plants exposed to a mixture at different combinations of 0.05 and 0.1 ppm. Both gases, singly (0.2 ppm) or jointly (0.05, 0.1 and 0.2 ppm) significantly depressed plant dry matter, yield and leaf pigments of tomato. The gases in all treatments consistently suppressed number of stomata and increased the width of their pores. The interactive effects of O3 and SO2 on dry matter and pore width were synergistic at 0.05+0.05, 0.05+0.1, 0.1+0.05 and 0.1+0.1 ppm, antagonistic at 0.2+0.2 ppm and more or less additive at 0.05+0.2 ppm and more or less additive at 0.05+0.2, 0.1+0.2, 0.2+0.5 and 0.2+0.1 ppm, respectively, in both years. The interaction for nubmer and size of stomata was antagonistic in those treatments, which caused synergistic effects on the rest of the assessments. A positive, invariant correlation was recorded in both years between widening of stomatal pores and percentage suppression in dry matter, yield, carotenoids and chlorophylls. Interactive effects of O3 and SO2 were dependent on the concentrations of the gases, e.g. the interaction was synergistic at 0.05 and 0.1 ppm but antagonistic at 0.2 ppm of both gases.

Technical note Influence of molecular structure of substituted benzothiazoles on corrosion inhibition and hydrogen permeation through mild steel in sulphuric acid

Abstract Aminobenzothiazole and three of its 6-substituted derivatives, namely 2-amino-6-chlorobenzothiazole (ACLBT), 2-amino-6-methoxybenzothiazole, and 2-amino-6-methylbenzothiazole, were synthesised and their inhibition of the corrosion of mild steel in 0·5M H2S04 was investigated by weight loss and some electrochemical techniques. Inhibition efficiencies of various concentrations of these compounds were determined at temperatures in the range 35–60°C. Of the four compounds, ACLBT showed the best performance, giving an inhibition efficiency as high as 97%, even at a very low concentration and at a temperature of 60°C. Potentiodynamic polarisation studies indicated that all four compounds acted predominantly as cathodic inhibitors, with adsorption from H2S04 solutions on mild steel surfaces obeying Temkins adsorption isotherm. All of the inhibitors were able to reduce hydrogen permeation through the steel surface and performance was enhanced by the addition of iodide ions. Auger electron spectroscopy a...

The interaction of SO2 and root-knot nematode on tomato

Intermittent exposure of tomato plants (cv. Pusa Ruby) to SO(2) at 286 microg m(-3) (3 h every heavy third day for 75 days) induced slight chlorosis of leaves. At 571 microg m(-3), considerable chlorosis with browning developed on the foliage. These symptoms were more pronounced and appeared earlier on SO(2)-exposed plants infected with Meloidogyne incognita race 1 (Mi), especially in post- and concomitant-inoculation exposures. Mi and/or SO(2) significantly reduced different parameters of plant growth. Synergistic (positive) interactions between SO(2) and Mi occurred in concomitant- and post-inoculation exposures at 286 and 571 microg m(-3), respectively. In other treatments, an antagonistic (negative) interaction was observed. However, in a few cases, additive effects of SO(2) and Mi were also recorded. Intensity of root-knot (galling) was enhanced at both concentrations of SO(2), while reproduction (egg mass production) of Mi was enhanced in concomitant-inoculation exposures at 286 microg m(-3) and inhibited at 571 micro m(-3). Exposure to SO(2) and/or Mi decreased the number and size of stomata but increased the number and length of trichomes on both the leaf surfaces. Stomatal aperture was significantly wider in the plants exposed to 571 microg SO(2) m(-3) alone and in pre-, post-, and concomitant-inoculation exposures at 286 or 571 microg m(-3). Stomatal aperture was directly related to foliar injury and reductions in growth, yield, and leaf pigments.

Effects of the root-knot nematode, Meloidogyne incognita, on the sensitivity of tomato to sulfur dioxide and ozone

Abstract Infection of plants with root-knot nematode leads to an increase in transpiration rate. We hypothesize that, in infected plants, the diffusive intake of gaseous pollutants would be greater and the interaction between the nematode and pollutant(s) would be governed by the degree of stomatal opening. Tomato plants infected with the root-knot nematode, Meloidogyne incognita were exposed to air containing 0, 50 or 100 ppb of SO2 or O3 for 5 h every third day on 27 occasions in 1988 and 1989. Plants exposed to the gases at 100 ppb had chlorotic and/or necrotic leaves, small shoots and roots, reduced leaf pigment levels and low yield, compared to untreated plants. Greater foliar injury developed on plants exposed to SO2 + O3 mixture. Symptoms were even greater on nematode-infected exposed plants. M. incognita alone reduced tomato yield by 14.4% and induced a 3.6% increase in the width of stomatal pores and a 15.6% increase in the transpiration rate. A positive correlation was observed between stomatal pore width and rate of transpiration. Interaction between SO2 and O3 depended on the presence (significant) or absence (insignificant) of nematodes. Most effects of nematode infection and gas exposures (especially mixtures) were synergistic. Disease intensity (galls per root system) was increased, but nematode reproduction (egg masses per root system, eggs per egg mass) reduced on plants exposed to SO2 and/or O3.

Comparative Damage Potential and Reproduction Efficiency of Meloidogyne Javanica and Races of Meloidogyne Incognita On Tomato and Eggplant

Plant damage potential and reproduction efficiency of Meloidogyne javanica (Treub) Chitw. and Races 1, 2, 3 and 4 of Meloidogyne incognita (Kofoid & White) Chitw. were compared in pot experiments with tomato and eggplant. M. javanica, on both hosts, caused greater plant growth suppression (pathogenic damage) than Races 3 and 4, but not greater than Races 1 and 2 of M. incognita. Root galling and egg mass indices of the species and races were similar, but there were differences between populations of females, number of eggs, total population densities and reproduction factors. The trends were the same on both the hosts. Total population, number of females and eggs, reproduction factor and fecundity were greatest for M. javanica followed by Race 2 of M. incognita. M. Javanica also produced larger females. Among the races of M. incognita, Races 1 and 2 had larger female populations, number of eggs, total population, reproduction factor, and fecundity than Races 3 and 4. The damage potential and reproduction efficiency can be arranged in the following order: M. Javanica > M. incognita Race 2 > M. incognita Race 1 > M. incognita Race 4 > M. incognita Race 3.

Effects of ammonia and root-knot nematode on tomato

Abstract Tomato plants inoculated with 2000 juveniles (JJ2) of root-knot nematode ( Meloidogyne incognita race 1) or intermittently exposed to 152 μg NH 3 m −3 exhibited significant suppression in growth, yield and leaf pigments compared with uninoculated or unexposed plants. However, NH 3 at 76 μg m −3 did not cause significant effects. The leaves of nematode-inoculated or uninoculated plants exposed to NH 3 (152 μg m −3 ) turned yellow in all treatments. Root galling and reproduction efficiency of M. incognita increased at 76 μg NH 3 m −3 but was suppressed at 152 μg m −3 . Fecundity, however, declined at both levels. The nematode and NH 3 interacted synergistically at 76 μg m −3 and antagonistically at 152 μg m −3 . Reductions in the plant growth, yield and photosynthetic pigments of the tomato were greatest in post- or concomitant-inoculation treatments at 152 μg NH 3 m −3 and concomitant inoculation treatment at 76 μg m −3 . Nitrogen content of foliage and roots increased significantly at both levels of the gas, being greater in post- and concomitant-inoculation treatments at 152 μg and 76 μg m −3 , respectively. Meloidogyne incognita or NH 3 decreased the number and size of stomata but increased the width of stomatal pores. Length and number of trichomes increased in the exposed plants, but remained unaffected in plants inoculated with the nematode alone. A positive correlation mostly occurred between width of stomatal pore and percent reduction in the plant growth, yield and leaf pigments of tomato.

Impact of sulphur dioxide exposure on conidial germination of powdery mildew fungi

The impact of sulphur dioxide, in two different concentrations (286 microg m(-3) and 571 microg m(-3)) for various exposure periods, on conidial germination of some powdery mildew fungi was investigated in artificial treatment conditions. SO(2) in general was inhibitory for conidial germination of all the studied powdery mildew fungi and the species did not differ much from each other in their sensitivity to SO(2). The per cent conidial germination was increasingly inhibited with an increase in the concentration of SO(2). The concentration of SO(2) and the exposure period were important determinants of the inhibitory effect.

Effects of sulfur dioxide on the development of powdery mildew of cucumber

Abstract Environment is a major factor that does influence host parasite relationships. Air pollution caused by SO 2 may directly alter the environment around the plant and pathogen. It is hypothesised that plants may respond differently to foliar pathogens in air polluted environments. To test this hypothesis, effects of intermittent exposures of SO 2 at 143, 286 and 571 μg m −3 were investigated on the development of powdery mildew of cucumber ( Cucumis sativa ) caused by Sphaerotheca fuliginea , using pre-, post- and concomitant-inoculation exposures in closed-top chambers. Sulfur dioxide (except 143 μg m −3 ) and the fungus acting alone caused chlorosis and/or necrosis, and mildew colonies on leaves, respectively and both reduced the plant growth and yield of cucumber. Fungus colonization was relatively greater on the plants exposed to 143 μg SO 2 m −3 , but at the higher concentrations, the colonies were greatly suppressed. Gas injury on fungus-infected plants was also less in the other treatments. Conidia of S . fuliginea collected from exposed plants varied in size. Conidial germination was considerably greater at 143 μg SO 2 m −3 . This concentration also promoted germination of the conidia exposed on glass slides. Higher concentrations (286 and 571 μg m −3 ), however, suppressed the germination of conidia from exposed plants or exposed on glass slides. The number of fibrosin bodies declined at all the concentrations. Synergistic effects of 143 μg SO 2 m −3 and S . fuliginea were recorded on plant growth and yield of cucumber. Sulfur dioxide at 571 μg m −3 and powdery mildew infection had an antagonistic effect on plant growth.